Keflex Dosage for Cellulitis
For adults with typical non-purulent cellulitis, the recommended dose of Keflex (cephalexin) is 500 mg orally four times daily (every 6 hours) for 5 days. 1
Standard Dosing Regimen
- Cephalexin 500 mg every 6 hours is the guideline-recommended dose for treating cellulitis in adults 2, 1
- The FDA-approved adult dosage range is 1-4 grams daily in divided doses, with 250 mg every 6 hours being the usual dose, though 500 mg every 12 hours may be used for skin and skin structure infections 3
- However, the IDSA specifically recommends the 500 mg four times daily regimen for cellulitis 1
Treatment Duration
- A 5-day course is as effective as a 10-day course if clinical improvement has occurred by day 5 2, 1
- Extend treatment beyond 5 days only if the infection has not improved 1
- This shorter duration recommendation represents a significant departure from traditional 10-14 day courses and helps reduce unnecessary antibiotic exposure 2
When Cephalexin is Appropriate
- Cephalexin is first-line for typical non-purulent cellulitis without systemic signs of severe infection 1
- It provides excellent coverage against streptococci and methicillin-susceptible Staphylococcus aureus (MSSA), the primary pathogens in cellulitis 1
- MRSA is an unusual cause of typical cellulitis, and β-lactam monotherapy with cephalexin is recommended in the absence of abscess, ulcer, or purulent drainage 2, 1
When to Consider MRSA Coverage Instead
Do not use cephalexin alone if any of these risk factors are present:
- Penetrating trauma (especially injection drug use) 2, 1
- Purulent drainage present 2, 1
- Evidence of MRSA infection elsewhere 2, 1
- Nasal colonization with MRSA 1
In these situations, add MRSA coverage with clindamycin, doxycycline, or trimethoprim-sulfamethoxazole to a β-lactam, or use clindamycin alone 2
Emerging Evidence on High-Dose Therapy
- A 2023 pilot trial compared high-dose cephalexin 1000 mg four times daily to the standard 500 mg dose 4
- Treatment failure occurred in only 3.2% with high-dose versus 12.9% with standard-dose 4
- However, minor adverse events were more common with the high dose 4
- This remains investigational and is not yet incorporated into guidelines, so standard 500 mg dosing remains appropriate 1
Critical Adjunctive Measures
- Elevate the affected extremity to promote drainage of edema 1
- Identify and treat predisposing conditions such as tinea pedis (toe web infections), venous insufficiency, lymphedema, or eczema 2, 1
- Examine interdigital toe spaces in lower-extremity cellulitis, as treating fissuring or maceration reduces recurrence 1
Common Pitfalls to Avoid
- Don't extend treatment to 10 days automatically - 5 days is sufficient if improvement occurs 1
- Don't add MRSA coverage routinely for typical cellulitis without risk factors 1
- Don't overlook underlying conditions that predispose to recurrent cellulitis 1
- Don't forget that blood cultures are unnecessary for typical cases of cellulitis 2
When to Hospitalize
Consider inpatient management if:
- Concern for deeper or necrotizing infection 1
- Severely immunocompromised patient 1
- Poor adherence to therapy expected 1
- Outpatient treatment is failing 1
- Systemic signs such as high fever, hypotension, or confusion 2